的镜头,投影到银幕上再加以评析。解像力的数值,仅仅是表示解像程度的数据而上,和解像的清晰度和反差的好坏没有关系。</P>
<> <img src="attachments/dvbbs/2005-5/2005530204833864.jpg" border="0" onload="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onmouseover="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.style.cursor=\'hand\'; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onclick="if(!this.resized) {return true;} else {window.open(\'attachments/dvbbs/2005-5/2005530204833864.jpg\');}" onmousewheel="return imgzoom(this);" alt="" />[/IMG]</P>
<> <B>2、反差</B>
摄影作品的鲜锐度,亦即明暗对比的程度。例如,黑与白的再现比很清晰,反差就大,不清晰时反差就小。解像度和反差都很大的镜头,具备高鲜锐度和高清晰度的优点
,就是一般公认的高性能镜头。</P>
<> <img src="attachments/dvbbs/2005-5/2005530204840597.jpg" border="0" onload="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onmouseover="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.style.cursor=\'hand\'; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onclick="if(!this.resized) {return true;} else {window.open(\'attachments/dvbbs/2005-5/2005530204840597.jpg\');}" onmousewheel="return imgzoom(this);" alt="" />
<img src="attachments/dvbbs/2005-5/2005530204848643.jpg" border="0" onload="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onmouseover="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.style.cursor=\'hand\'; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onclick="if(!this.resized) {return true;} else {window.open(\'attachments/dvbbs/2005-5/2005530204848643.jpg\');}" onmousewheel="return imgzoom(this);" alt="" /> </P>
<> <B>3、MTF[modulation transfer function]</B></P>
<> MTF是modulation transfer function的头一个字母的简称,是一种测定镜头反差再现比或鲜锐度的镜头评估方法。音响设备之类的电气系的特性评估时,有所谓周率特性
面整体的MTF特性一目了然。</P>
<> <img src="attachments/dvbbs/2005-5/2005530204855213.jpg" border="0" onload="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onmouseover="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.style.cursor=\'hand\'; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onclick="if(!this.resized) {return true;} else {window.open(\'attachments/dvbbs/2005-5/2005530204855213.jpg\');}" onmousewheel="return imgzoom(this);" alt="" />
</P>
<> <B>4、各种MTF特性</B>
MTF特性图中,横轴为以画面中心0开始的像高,纵轴为反差大小,MTF特性以10线/mm和30线/mm来表示。测试表的空间频率数,镜头的光圈值、画面上的方向等都揭示在以
镜头,两者的平衡固然重要,一般而言,10线/mm的MTF特性在0.8以上属于优秀镜头,。S和M的特性如果一致的话,松蒙的影像也会以自然的形状呈现出来。</P>
<> <img src="attachments/dvbbs/2005-5/200553020492473.jpg" border="0" onload="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onmouseover="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.style.cursor=\'hand\'; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onclick="if(!this.resized) {return true;} else {window.open(\'attachments/dvbbs/2005-5/200553020492473.jpg\');}" onmousewheel="return imgzoom(this);" alt="" />
胶片制造厂商,彩色胶片发色特性设计基准的数值。换句话说,如果不是和ISO标准镜头的透光特性的镜头,彩色胶片就无法获得厂商所设计的发色品质。</P>
<> <img src="attachments/dvbbs/2005-5/200553021272833.jpg" border="0" onload="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onmouseover="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.style.cursor=\'hand\'; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onclick="if(!this.resized) {return true;} else {window.open(\'attachments/dvbbs/2005-5/200553021272833.jpg\');}" onmousewheel="return imgzoom(this);" alt="" />
<B>7、周边光量[Peripheral illumination]</B></P>
<P> 镜头明亮度取决于F值(即光圈值),这表示在镜头的光轴上,也就是画面中心的影像的明亮度。到于书面旁边的明亮度(像面的照度),则称为周边光量,以百分比来表
示。周边光量因受到镜头渐晕现象及余弦四次方定律的影响,与中心部相比,明亮度必然减少。
<img src="attachments/dvbbs/2005-5/2005530212721632.jpg" border="0" onload="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onmouseover="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.style.cursor=\'hand\'; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onclick="if(!this.resized) {return true;} else {window.open(\'attachments/dvbbs/2005-5/2005530212721632.jpg\');}" onmousewheel="return imgzoom(this);" alt="" />
<B>8、渐晕现象[Vignetting]</B>
投射到画面旁边的光线,没有全部通过有效口径(即光圈直径),被光圈前后的镜片框所遮挡,因而导致周边部光量低落的现象。这种现象只要缩小光圈即可消除。
<img src="attachments/dvbbs/2005-5/2005530212753848.jpg" border="0" onload="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onmouseover="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.style.cursor=\'hand\'; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onclick="if(!this.resized) {return true;} else {window.open(\'attachments/dvbbs/2005-5/2005530212753848.jpg\');}" onmousewheel="return imgzoom(this);" alt="" />
<B>9、余弦四次方定律[Cos4law]</B>
即使视角很广,完全没有渐晕现象的镜头,它的周边光量仍然比书面中心少。画面周边的影像,是经由和光轴有着某种倾斜角度的入射光束所形成的,它的明亮度和倾斜
积比),就可以防止周边光量的降低。</P>
<P> <img src="attachments/dvbbs/2005-5/200553021281242.jpg" border="0" onload="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onmouseover="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.style.cursor=\'hand\'; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onclick="if(!this.resized) {return true;} else {window.open(\'attachments/dvbbs/2005-5/200553021281242.jpg\');}" onmousewheel="return imgzoom(this);" alt="" /></P>
<P> <B>10、遮蔽[shading]</B></P>
<P> 最典型的例子是,由于遮光罩的前端或滤片框把射入镜头的光线遮掉一部份,使得画面角落的影像发暗,或画面整体变淡的现象。原本是指应该进来的光线,因为受到某
生,使用遮光罩遮挡有害光线,摄影时利用景深钮的功能,在实际光圈下确认画面的情况,是预防鬼影出现的不二法门。</P>
<P> <img src="attachments/dvbbs/2005-5/2005530212825166.jpg" border="0" onload="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onmouseover="if(this.width>screen.width*0.7) {this.resized=true; this.width=screen.width*0.7; this.style.cursor=\'hand\'; this.alt=\'Click here to open new window\nCTRL+Mouse wheel to zoom in/out\';}" onclick="if(!this.resized) {return true;} else {window.open(\'attachments/dvbbs/2005-5/2005530212825166.jpg\');}" onmousewheel="return imgzoom(this);" alt="" /></P>
<P> <B>13、镀膜[coating]</B></P>
<P> 光线在射入或射出镜片时,由于折射率的不同,在各个镜片与空气界面上,约有5%的光线反射出去。这不单单是镜片的透过光线减少而已,表面的重复反射也是造成光斑